1. Technical Field
The present invention relates to a light amount correcting method for a light emitting apparatus, an image forming apparatus, and a display apparatus
2. Related Art
An image forming apparatus such as a copier using line heads constructed by arraying a plurality of light emitting devices in a line as exposure units has been developed. With respect to the image forming apparatus, there has been proposed a technique for suppressing occurrence of a change in brightness caused from deterioration in characteristics of the light emitting devices or a variation of brightness caused from deterioration of lightening over the entire heads.
In order to solve the problem, a technique for measuring a variation in light amount and adjusting voltages, current, and light emitting time for pixels so as for the light amounts to be uniform is disclosed in, for example, JP-A-59-194566. On the other hand, a technique for detecting light amounts with optical sensors and correcting the light amounts based on the detected light amount values is disclosed in, for example, JP-A-60-107373. In addition, a technique for counting light emitting times for the pixels with a counter and correcting the light amount based on the counted light emitting times is disclosed in JP-A-62-246753.
However, in tone technique disclosed in JP-A-59-94566, the light amount correction value for a pixel having a small light amount greatly increases so as for the light amount to be uniform in comparison with a pixel having a large light amount. Therefore, the deterioration of the pixel becomes as large as the correction value. In addition, since a large number of bits of the correction value are required so as for the light amount to be uniform, a size of a circuit becomes large. On the other hand, in the technique disclosed in JP-A-60-107373, since the light sensor is provided to each of the pixels, production cost increases. In the technique disclosed in JP-A-62-246753, since the counter is provided to each of the pixels, production cost also increases.